1. Technical Field
The invention relates to solar cells, and more particularly, to a solar cell testing system, a solar cell testing method, and a multifunctional testing light source.
2. Related Art
Existing minerals that may be used to generate electricity, such as crude oil and coal, are being exhausted. Furthermore, thermal power plants have been exacerbating global warming. As a result, it is critical for the human being to develop and promote alternative energy that is sustainable. Among all potential sources of sustainable alternative energy, solar energy is a kind that's relatively more popular.
Not only do suppliers try to enhance solar cells' conversion efficiency, but conversion efficiency is also used to evaluate the quality of solar cells. For example, a 0.2% difference in conversion efficiency may lead to a huge disparity in price.
Suppliers frequently use artificial light sources to simulate sun light defined as AM1.5G in order to determine solar cells' conversion efficiency. Specifically, these artificial light sources may simulate the situation that the sun light incidents from an angle 48.2 degrees away from the vertical angle (i.e. zenith angle). However, artificial light sources seldom can match the AM1.5G specification exactly. Inevitably, this causes the tolerance for errors to be relatively large. For example, as defined by the IEC60904-9 standard, as long as a light source has less than 25% deviation in energy within each and every predetermined light band, the light source may be certified as a class-A light source. Because of the loose requirement, several class-A AM1.5G light sources may have quite different spectra. For example, one of the light sources may have relatively more energy in the band of blue light, while another light source may have relatively more energy in the band of red light. These light sources may not be sufficient to enable the determination of whether a solar cell has a 0.2% deviation in conversion efficiency.
Regardless of whether a single class-A light source or a plurality of class-A light sources are used, when the testing result indicates that two solar cells have the same conversion efficiency, the two cells may still have different spectral responses on different light bands. For example, one of the solar cells may have relatively stronger response to blue light, and the other may have relatively stronger response to red light. If these two solar cells are connected in series, they will hinder each other's performance regardless of whether the series circuit is receiving light with relatively more energy in the blue or red band. In other words, because of the mismatch between the two solar cells, the series circuit may not have optimal performance in supplying photo current.
To avoid errors in classification, a solar-cell supplier may measure a solar cell's spectral response additionally, and then infer the solar cell's quantum efficiency (QE). However, conventional methods of measuring spectral response are not only slow but also costly. As a result, the methods are not popularly used on solar cell production lines.
Therefore, solar cell suppliers likely will be interested in artificial light sources that not only may simulate AM1.5G light more precisely but also have smaller inter-machine variation. These suppliers likely will also be interested in methods and testing systems that may measure a solar cell's spectral response at a high throughput and low costs.